Molecular dynamics simulation on the Thermosinus carboxydivorans pfl ZTP riboswitch by ligand binding.

Riboswitches are RNA molecules that can regulate gene expression which is affected by ligand-binding during cotranscriptional folding process. However, the role of ligand during the folding is still unclear. In this study, the pfl domain of Thermosinus carboxydivorans ZTP riboswitch was discussed. The ligand is molecule ZMP. We mainly analyzed the change of ZMP-free and ZMP-bound aptamer domain by the dynamics simulation method. Structural features by calculating their RMSD, RMSF, etc. are analyzed. The results demonstrate that the binding domain require the presence of ZMP to maintain a stable fold. It also suggested that ZMP specificly binding to ZTP can generate more hydrogen bonds in the binding domain. Through the calculation of binding free energy decomposition of each nucleotide, molecule ZMP was found to promote the recognition and binding process of ligands by controlling some special nucleotides in the process of ligand binding. At last, the dynamical correlation and components of conformational motions were both applied to explore the effect of molecule ZMP to ZTP riboswitch. In general, ZMP can effectively affect the motions of the pfl riboswitch and facilitate the folding process of the ZTP riboswitch.These results may provide some new ideas for structural changes in riboswitches and their cotranscriptional folding process.

[Summary on international quality standards of Bupleuri Radix].

Bupleuri Radix is a traditional staple Chinese medicinal material which has a wide range of medicinal values. However, with the increase of the international trade of Bupleuri Radix, its quality and safety issues have attracted much attention. Therefore, the establishment of international standards for Bupleuri Radix has important practical significance. In view of this, based on our foundation work on the standardization of Chinese medicine and international standards, this review systematically collates the quality standards of the major countries(regions) in which Bupleuri Radix is used, including the origin, macroscopic characteristics, microscopic characteristics, determination of marker compounds and extrinsic harmful contaminants. The existing problems and suggestions are also discussed in this review, which may provide reference for the study of the quality standard of Bupleuri Radix.